With wast heat boilers there is usually a difference in gas flow cross-sectional areas as between the waste gas duct and the boiler inlet duct. Therefore the two must be joined by an expanding transition chamber.
This transition chamber can comprise a steel casing to contain the gas pressure and lined with refractory material to keep the steel casing at an acceptable metal temperature. This design has many disadvantages, particularly at high gas temperatures. Some of its disadvantages are the need for a high degree of maintenance of the refractory, the possibility of the refractory breaking away and exposing the steel shell to hot gases and the possibility of the refractory cracking and allowing hot gases to condense on the casing thus leading to corrosion.
The invention has therefore been made with these problems in mind and so it is an object of the invention to provide a transition chamber and waste heat plant where these problems are avoided.